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Coherent dynamics of a Josephson charge qubit

T. Duty, D. Gunnarsson, K. Bladh, P. Delsing

DOI 10.1103/PhysRevB.69.140503 · Physical Review B

T1

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Abstract

We have fabricated a Josephson charge qubit by capacitively coupling a single-Cooper-pair box (SCB) to an electrometer based upon a single-electron transistor (SET) configured for radio-frequency readout (rf-SET). Charge quantization of 2e is observed and microwave spectroscopy is used to extract the Josephson and charging energies of the box. We perform coherent manipulation of the SCB by using very fast dc pulses and observe quantum oscillations in time of the charge that persist to ≃10ns. The observed contrast of the oscillations is high and agrees with that expected from the finite EJ/EC ratio and finite rise time of the dc pulses. In addition, we are able to demonstrate nearly 100% initial charge state polarization. We also present a method to determine the relaxation time T1 when it is shorter than the measurement time Tmeas.

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FormulaReported Tc (K)Pressure (GPa)Type
Al

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—Pressure not reportedunknown

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